The blade was created with 666 melted angels, bearing their power and resentment; as a result the sword does not inflict fatal injuries, but has the power to weaken and seal creatures.
they can return to normal once they have accumulated enough power.

A sword that can cut through almost every known material with ease but each time you draw it, you must draw blood with its blade or else it cannot be returned to its scabbard and will slowly cause you to fall into madness.